Management of pain in the Emergency Department (ED) is a major nursing and medical challenge. Inadequate ED pain management has been well documented. Opioid analgesics constitute the standard treatment of acute pain, however there are numerous obstacles to optimal use of opioids in the ED. These obstacles include high patient-to-staff ratios, the simultaneous demands of acutely ill patients, large inter- individual variability in opioid requirement, dose related toxicity, and lack of resources to provide individualized pain management. Patient Controlled Analgesia (PCA) has been used successfully in post-operative pain management. In that setting, patients typically receive titration of morphine until the patient is comfortable and then PCA is initiated. Given the barriers to delivering this intensive management in the ED, PCA has the potential to improve pain management by allowing an initial bolus dose of opioid to be administered to all patients, followed by patient-initiated demand dosing. This regimen is a novel means to bridge the gap between pain relief from an initial, often inadequate dose and that desired by patients with higher analgesic requirements. It can also be used to maintain analgesia over time for patients with extended ED stays. PCA has had minimal application in the ED;and few studies have rigorously assessed its impact on efficacy and safety. The aims of the study are to: 1) assess the efficacy and safety of PCA in the ED;and 2) compare two PCA dosing regimens. 210 ED patients ages 18 through 65 years with abdominal pain requiring intravenous opioid analgesia will be enrolled in a randomized double-blind placebo-controlled study. All patients will receive a loading dose of 0.1 mg/kg morphine. They will then receive either: 1.0 mg, 1.5 mg of morphine or placebo PCA demand dosing available every 6 minutes. A numerical rating scale recorded every half hour up to 2 hours after initial administration of morphine will be used to measure pain intensity. Oxygen saturation, respiratory rate, and systolic blood pressure will be monitored continuously by the study nurse. All patients can receive morphine supplementation as needed at the discretion of the clinical staff. Primary endpoints are change in pain intensity from baseline to 30 minutes and incidence of adverse events. Pre-planned comparisons between the groups will be performed following analysis of variance. Multivariate statistics will be used to adjust for baseline differences should they occur. Secondary endpoints are pain over the total two hour observation period, number and dose of additional analgesics administered by the clinical staff, incidence of nausea, vomiting, and pruritis. We hypothesize that PCA will provide superior analgesia without a greater incidence of adverse events than a single dose that can be supplemented at the discretion of the clinical staff;and that demand dosing of 1.5 mg will be superior to 1.0 mg without more adverse events. The application of PCA to the ED constitutes a novel and promising approach to improving pain management in this challenging environment. PUBLIC HEALTH RELEVANCE: This study aims to provide preliminary data about the safety and efficacy of patient controlled analgesia for management of abdominal pain the Emergency Department. It represents a novel approach to managing pain in this busy and demanding setting.